Automobiles utilize safety restraint systems to protect vehicle occupants. The restraint systems may include restraints, such as front airbags, side airbags, and seat-belt pretensioners. The restraint systems typically include passive accelerometer-based collision severity sensors, which are used to gather information for control and deployment of the restraints. A controller within the restraint systems performs calculations to differentiate between a collision event for which deployment or non-deployment of a restraint is desired. In general, this differentiation is most difficult to perform during vehicle-to-vehicle offset type collisions and oblique type collisions, mainly due to the difficulty in the detection of these collisions.
Depending upon the particular collision sensor scheme, post-collision sensors may utilize from approximately 5-20 ms of post-collision time to obtain, process, and transmit collision data during an approximate 48 kmh equivalent fixed barrier collision. For non-barrier collisions of equivalent severity, longer data times may be utilized.
Sensing and deployment control systems that are used in the activation of safety systems tend to utilize single-point or dual-point collision sensors to detect a collision. The collision sensors are typically in the form of solid-state accelerometers that are located in a vehicle compartment, such as in a dashboard, in a tunnel location, behind a bumper, or on a radiator support. The accelerometers are used to detect collision conditions early on in a collision event and provide information related to the collision severity. Various algorithms are then utilized to evaluate the collision conditions and the collision severity for the deployment of safety systems.
The algorithms utilize accelerometer information, collected early in a collision event and in response to a collision, to determine timing for deployment of restraint systems. It is desirable in the deployment of the restraint systems to prevent inappropriate deployment timing or inadvertent deployment of the restraint systems. Thus, deployment thresholds are often set in response to the type of collision and the associated conditions thereof.
Special collision events such as low speed barrier collisions, pole collisions, and various vehicle-to-vehicle collisions provide the greatest challenges for collision sensor design, and collision type determination. The term “collision type” generally refers to the location on a host vehicle that is involved in the collision and may include other related information. A collision type may for example refer to whether a particular collision is a full-frontal, an oblique, or an offset collision, as well as include information related to relative location, and collision change in velocity of an object of concern. Oblique type collisions are generally more difficult to detect compared to a full or head-on collision.
Sensor and algorithm design criteria of a countermeasure system ensure that the performance of a sensing system satisfy timing requirements for various different collision types and also have the capability of appropriately maintaining safety systems in a deactivated state during non-deployment conditions. Thus, there exists a need for an improved post-collision sensing system and method for detecting a collision type and appropriately activating safety systems. It is further desirable to provide a system that is inexpensive to manufacture, such that it may be readily used in various vehicle platforms.